Safety shear-pin drive



March 30,'1948. F. H. NICKLE ETAL 2,438,676

SAFETY SHIEAR-PIN DRIVE Filed Dec. 3 1, 1943 INVEZORS Patented Mar. 30,1948 SAFETY SHEAR-PIN DRIVE Frank H. Nicklev and Arthur Cr. Nickle,Saginaw, Mich.

Application December 31, 1943, Serial No. 516,556

(Cl. (S4- 28) 10 Claims.

This invention relates to a safety driving mechanism for power drivingmachines that require a shearable pin for drivingly connecting twomoving machine elements, one of which elements must stop instantly toavoid damage when fouled or over-loaded. A specificV application is theEar corn crushing machine disclosed in U. S. Letters Patent No.2,330,139 granted to us under date of September 21, 1943, because suchmachines frequently encounter tramp metal, or other uncrushablematerial, in the ear corn or small grain supplied thereto.

The conventional shear-pin is usually driven tightly into its supportingelements, whereby it becomes a troublesome and time-consuming job toremove the pieces after the pin is ruptured, and to drive a new one inits place. An object of this invention is to provide a shear-pin that isa slip fit in the supporting elements, and is yieldably held in workingrelation with the shearing elements, so that the broken pieces of theruptured pin may be readily displaced by theV new pin without the use ofhand tools.

Another object is to provide a reversible shearpin having a reduced orweakened cross section, at the predetermined point of shear, that willregister in proper relation to the shearing elements, regardless as towhich end of the pin is in engagement with the yeldable holding means.

In the drawing:

Fig. 1 is a longitudinal cross-sectional View showing the application ofthe safety shear-pin mechanism to a grooved pulley, the assembly beingmounted on a shaft that drives a machine.

Fig. 2 is a fragmentary end View showing the pulley, shear-pin collarassembly, and the shearpin holding means.

Fig. 3 is an end View of the shear-pin collar and the shear-pin holdingmeans.

Fig. 4f is an edge view thereof.

Fig. 5 is an isometric View. of a clamping block used to secure thespring in place.

Fig. 6 is an isometric view of the U-shaped spring that is adapted tohold the. shear-pin in working relation in the assembly.

Fig. 7' is an enlarged detail view ofthe shearbin.

Referring to the drawing, in which we have shown the preferredembodimenty of our invention, the numeral Il? indicates the drive shaftof a machine (not shown), and on which a pulley l rotatably mounted,thisV pulley being driven from any convenient source of power. Formedintegral with the pulley II is a hub I2 havingY a plurality ofcircumferentially spaced apertures I3 that are aligned parallel to theshaft and on the same radius. The pulley is held against axial movementon the shaft by means of a conventional set collar I 4 on one side, anda shear-pin collar I 5 on the opposite side, the shear-pin collar beingsecured on the shaft by means of the key and set screw IE and I'Irespectively.

The shear-pin collar .I5 can be of any desired shape, and is providedwith an aperture I8 that also parallels the shaft IIJ on the same radiusas the apertures I3, thus making it possible to rotate the pulley Ilwith respect to the shaft It so the aperture I8 will register with oneof the apertures I3 to accommodate the shear-pin I9, thereby providingmeans whereby rotative movement may be transmitted from the pulley tothe shaft or contrawise.

The shear-pin l@ is formed as shown in Fig. '7,

it being preferably but not necessarily cylindrical in shape, and havingfrusto-conical or tapered ends 2i! that may be easily inserted into theapertures I3 and 18. At the shearing point in the middle of the pin isan annular groove or undercut 2| that reduces the cross-sectional area,and consequently weakens the strength of the pin, the reduced area beingaccurately gauged to transmit the driving torque necessary for thenormal operation of the machine, ibut which will fail by shear when anyunusual resistance is encountered which might otherwise damage themachine. On both sides of the shearing point 2|, and equidistanttherefrom, is an annular groove or undercut 22 that provides a seat forthe holding means that will be presently described.

lThe shear-pin holding means, illustrated in Fig.V 6, is preferably aU-shaped yeldable spring having` parallel legs 23, a bighted end 24and-the opposite ends 25 bent at right angles to the legs. Whenassembled on the shear-pin collar I5, the legs 23 are held againstoutward lateral movementby two similar separator blocks 26 that aregrooved as at 2'!A to seat the legs. The centrally disposed hole 28 inthe separator block accommodates the screw 29 threaded into the collarI5. The spring is held against longitudinal movement in one direction bylooping the bighted end 24 around either one of the screws 29, andagainst movement in the opposite direction by the bentv ends 25 whichhook over the edge of collar I5 as shown in Fig. 4.

A circular hanged cover plate 36 is provided as a safety guard againstaccidents when the shear-pin collar is in motion, this cover plate beingmounted over the outer face of the shear-pin collar and secured theretoby screws 23Y and 3l or other means. The aperture 32, through which thenew shear-pin is introduced into the shearpin collar, is made largeenough to permit the operator to see or feel if the legs 23 of thespring are properly seated in the groove 22 of the shearpin. Otherwise,the shear-pin might be inadvertently misplaced so that it could notshear off at the weakened shearing point. In this case, the purpose ofthe shear-pin would be defeated.

It will be further noted that the inner face of the shear-pin collar I5is provided with an annular shoulder 33 that spaces the shear-pin collarfrom the adjacent face of the pulley hub and forms a clearance space Stherebetween, the object of which is to preclude the possibility ofscoring theface of either the shear-pin collar or the pulley hub, shouldthe fracture of the shear-pin with respect to the shaft to realign theaperturesY I8 and I3, and then displacing or ejecting the rupturedpieces of the shear-pin by simply forcing a new pin into place, theabutting frusta-conical endsefV the old and new pins being axiallyaligned so the new pin can be readily pushed between the yieldable legs23 of the spring. As the shear pins are symmetrical with respect to theshearing pointit will be apparent that they Yare reversible,therebyreliminating the possibility of the pin being installed wrong endto by an inexperienced operator.

What we claim is:

l. A reversible safety shear-pin adapted for transmitting movement froma driving element to a driven element by a force applied at right anglestothefshear-pin, a body having its middle section undercutfat theYpredetermined point of shear, end sections Aformed with a groovepositioned equidistant from the predetermined shearing point, eithergrOve being adapted to seat a pair of yieldable 4elements for holdingthe shear-pin in fixed relation VwithY its supporting elements, andmeans that facilitate pushing the shear-pin between the yieldableholding elements, said means comprising frusta-conical ends thereon.

2. The combinationof a drive shaft, a pulley rotatably mounted on theshaft, means secured to the shaft for Apreventing axial movement of thepulleysai`d means including a shear-pin collar having a. Vshear-pinaperture parallel to the shaft, a similar aperture on the same radius inthe pulley Astructure that is alignedY concentric with the collaraperture, a safety shear-pin seated in the aligned apertures, yieldablemeans for holding the shear-pin in working relation with pulley andcollar, and a removable cover secured to the shear-pin collar forprotectingY the yieldable `shear-pin holding means, said cover having anopening through which theV shear-pin is introduced-into the shear-pinapertures.

Y 3. YA safety driving means for transmitting r0- the unshearedshear-pin'in proper relation there..

with, said holding means comprising a bifurcated element that straddlesthe shear-pin and seats in opposite sides of the annular groove.

4. In a shear-pin collar assembly adapted for mounting on a shaft forrotation therewith, a collar having an aperture adapted to seat ashearpin, said pin projecting unequally therefrom on the two sidesthereof, means engaging the shorter projecting end for holding the pinin working relation with the collar, and a circular disk thatV coversthe collar and shear-pin holding means, said disk being rigidly securedto the collar for rotation therewith.

ing a pair of axially aligned rotatable elements, one of which issecured to a shaft, the said pinV having a cylindrical body withfrusto-conical shaped ends, an undercut intermediate its length to forma shearing point, and a groove near each tativeV movement from adrivingmember to a driven member axially aligned therewith, saidA end that isadaptedto engage means carried by the element that is secured to theshaft for holding the pin in working relation for drivingly connectingthe said elements, said grooves being spaced equidistant from theshearing point.

'7. In combination, a shaft, a pulley rotatably mounted on the shaft, ashear-pin collar mounted adjacent to the pulley hub and secured to theshaft for rotation therewith, axially aligned apertures in the pulleyhub and collar on the same radius, a reversible shear-pin withfrusto-conical ends seated in the aligned apertures, said pin having amiddle section undercut at a predetermined shearing point and a groovein each end section that is spaced equidistant.

from the shearing point, and yieldable means engageable with either endgroove for Vholding the Ypin in a predetermined position until it isruptured by shear.

Y 8. In combination, Ya shaft, a pulley rotat-V ably mounted on theshaft, a Yshear-pin collar secured to the shaftk for rotation therewith,a shear-pin in driving engagement with the pulley and shear-pin collar,means for holding the shear-pin in working relation with the pulley andcollar, and a vcircular guard for covering the collar and shear-pinholding means, said guard having an aperture through which the shearpinmay beV introduced into the holding means.

9. A safety driving `means for transmitting rotative movement from adriving member to'a driven member axially aligned therewith comprising,a cylindrical shear-pinformed with an* shorter projecting end forholding the ypin in.K

5 6 Working relation with the collar, and a circular disk that coversthe collar and shear-pin hold UNITED STATES PATENTS ing means, said diskbeing formed with an opening through which the shear pin may be intro-Number Name Date duced. into the shear-pin collar. 5 525,419 Hoyt Sept-4, 1394 FRANK H NICKLE 1,778,477 WOOd Oct. 14, 1930 ARTHUR G' NICKLE.1,849,174 Carter Mar. 15, 1,932 1,870,153 Thoman Aug. 2, 1932 2,128,715Reich Aug. 30, 1938 REFERENCES CITED 10 2,298,316 simmons oct. 13, 1942The following references are of record in the 2,307,556 Wileman Jan. 5,1943 le of this patent:

